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MSP430FR2153: GPIO current limit and impedance

MarcB
Genius 11160 points
Part Number: MSP430FR2153

Can you please help to answer the following question that came up during the design phase?

We supply an EEPROM with three pins of the MCU (P3.0-3.2). These are switched on together and must supply a maximum of 3mA.

Do you recommend using series resistors (as in the diagram 220R below) to limit the maximum current and thus protect the inputs?

How high do you specify the output impedance of these pins for a DVCC of 3.0 or 3.3V?



Thank you!

  • 0
    TI__Genius 12615 points

    Hi Marc,

    If you're supplying the current to the EEPROM, you should be able to drive 2-3mA from each GPIO.  I don't know that you would need the additional resistors to limit the current if the EEPROM isn't going to draw it.  (I'm assuming the datasheet of the EEPROM indicates is will draw less than 3mA at 3.3V.)  If you look at the notes under Table 5-12 in the datasheet, you'll see that the max current which can be supplied from all GPIOs combined is 48mA.

    BR,
    Leo

  • 0 in reply to Leonardo Estevez
    Prodigy 40 points

    Hello Leonardo

    Thanks a lot for your answer. This question originally comes from me.

    As you mentioned the datasheet of the EEPROM specifies a max. supply current of 3mA for read or write (see table below).

    So you see no need for these series resistors, even if there is a decoupling capacitor used at the VCC pin of the EEPROM between 10...100nF?

    Thanks for your support and kind regards,

    Ueli

  • 0 in reply to Ueli Schraner
    TI__Genius 12615 points

    Hi Ueli,

    There may be some impact to internal analog component readings when drawing a burst of current to energize external parts. From that perspective, I would recommend some small resistors between the GPIO pins and the powered device.

    BR,
    Leo

  • 0 in reply to Leonardo Estevez
    Prodigy 40 points

    Hi Leo

    Thanks for your answer.

    For that reason we already lowered the decoupling capacitor at the EEPROM from 100nF to 10nF, which is still fine for the EEPROM.

    In addition, we have the 220R series resistors at the GPIO pins to be sure.

    Best regards,

    Ueli

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